Does one have to close his nose in order to prevent unforced nasal sound from occurring?

َQuestion
Salaam. Does one have to close his nose in order to prevent unforced nasal sound from occurring? E.g. in الَّذِيت that one closes his nose (without touching it) so that there is no `Ghunna` occurring in the ال.
If you could please elaborate. Jazaak Allah
Answer
Wa alaikum assalaam wa rahmatullahi wa barakaatuh
To rid oneself of an unwanted ghunnah we need to focus the sound out of our mouth and not let it go up through the back of the nasal passage.  Sometimes if a letter is weak, the sound goes up through the nose instead of out the mouth, and an unwanted ghunnah accompanies the weak letter .  
The ghunnah is always present in the نون and the نون  and لام share the front tip and the gums of the two front upper teeth in articulation points.  If one does not use the last third of the side of the tongue until it ends at the tip of the tongue for the لام it is going to sound like a نون and therefore have a ghunnah.  We have to be careful to spread out tongue and use its sides (last third) until they end at the tip.  It is a U shaped articulation point. 
Wa iyyakum